What is the origin of the idiom "hear a pin drop" and when to use it?

The exact origin of the idiom "hear a pin drop" is challenging to trace, but it likely emerged from the idea that a room or environment is so quiet that the sound of a pin falling to the ground would be distinctly audible. This expression is used to describe an environment or situation where there is an exceptionally deep and complete silence, typically to emphasize the quietness of the surroundings.